Fans won't start on my compaq evo

This is a desktop
Compaq Evo D300s PC Desktop (comes in 3 forms)
SFF
mini
full
answering for FULL.
with HP
244166-001 power supply 24pin it is.

the fans are 12vdc fans, all 3. if all 3 are dead that told you its not 3 bad fans is 1second flat
the 12vdc is missing if the fans are 2 wire the BIOS can not detect
only 3 wire fans BIOS can detect, and most this pC DO NOT.
un-like our high end desktops can (ASUS is tops)
the PSU is bad or not plugged in to the wall,
or the rear of PSU some have 0/1 switch there turn it to "1" = on.
there are more symptoms here.

push power do you hear the HDD motor spin up)
it too is 12vdc motor and guess what, if silent the PSU is dead.
there is ) exceptions to this , they are.
1: the MOBO has short. unplug hdd, and dvd drive, first. to clear shorts from them.
2: mobo dead.
3 : the PSU monitors for power, and if any of its outputs fail it shuts down, to save blowing up expensive chips.

If any of the PSU outputs go dead , PSU shuts down/.
if any of the PSU outputs short, (loads shorted) it shuts down.
what I do is bench test the PSU.
our unplug it, and use the jumper wire seen here.
Jump pin 16 to 17 on newer PSU. 24pin
this turns it on, and see if the PSU fan turns
http://www.pcdied.com/power.html
go here see word jump

I'm assuming one of the 3 fans not turning is PSU fan 1.
right? (says 12vdc is gone or PSU is overloaded or bad)
once jumped 2 pins check for correct voltage on all pins.
with a voltmeter , DC volts. per link above, documents all that.

one other test is the dvd eject button if dead the PSU is bad or shut down for cause.

I suggest replacing the fans with new fans. Fans do expire and they need to be replaced.